November 21, 2012

More Evidence Shows Evolution Of Birds From Dinosaurs

More evidence has emerged, published in the journal Current Biology, claiming birds are the descendants of dinosaurs.

The prehistoric Archaeopteryx and bird-like dinosaurs before them had a more primitive version of a wing, according to the recent findings.

Scientists are piecing together how the wing evolved, lending to evidence that gliding dinosaurs spent much of their days in the trees.

"Before, it seemed that we had more or less modern wings from the Jurassic onwards," Nicholas Longrich of Yale University, said in a statement. "Now it's clear that early birds were more primitive and represented transitional forms linking birds to dinosaurs. We can see the wing slowly becoming more advanced as we move from Anchiornis, to Archaeopteryx, to later birds."

Anthony Russell of the University of Calgary said these findings make scientists rethink the aerial capabilities in the early phases of avian evolution.

The scientists made this discovery while looking very carefully over the fossil evidence that neither the wings of bird-like dinosaurs nor the wings of the very early bird Archaeopteryx looked quite like those of modern birds. The team found the feathers on their wings had a different configuration.

"Archaeopteryx has this weird design with multiple layers of long flight feathers," Longrich said in the statement. "The dinosaur Anchiornis has tons of simple, strip-like feathers that overlap–the only bird that has anything remotely similar is a penguin."

The researchers indicated early wings probably worked effectively as airfoils for gliding and, perhaps, for primitive flapping at higher speeds.

The feathers on the primitive wings couldn't separate and twist in the way a modern bird's might. Also, low-speed flight and ground takeoff may have been difficult for them.

Scientists on the project believe the wing feather arrangement seen in modern birds may have evolved within a period spanning about a few tens of millions of years, and then remained largely unchanged for the last 130 million years.

"We are starting to get an intricate picture of how feathers and birds evolved from within the dinosaurs," colleague Jakob Vinther from the University of Bristol said in the statement. "We now seem to see that feathers evolved initially for insulation. More complex vaned or pinnate feathers evolved for display. These display feathers turned out to be excellent membranes that could have been utilized for aerial locomotion, which only very late in bird evolution became what we consider flapping flight."

He said the display features turned out to be excellent membranes that could have been utilized for aerial locomotion. Vinther added the new research is shedding light not just on how birds evolved to fly, but on how feathers came to be the way they are now.